Forced Convective Flow Drag and Heat Transfer Characteristics of CuO Nanoparticle Suspensions and Nanofluids in a Small Tube

The present experiment investigates the forced convective flow drag and enhanced heat transfer of water−CuO nanoparticle suspensions and nanofluids in a steel tube with an inner diameter of 1.02 mm. The nanoparticle suspension consists of a base fluid and nanoparticles, while the nanofluid consists of a base fluid, nanoparticles, and a surfactant. Previous studies were all concerned with nanofluids without any research attention paid to nanoparticle suspensions yet. The effect of fluid temperature on heat transfer and flow drag has never been considered as well. This study aims to understand how surfactant and fluid temperature affect forced convective flow drag and heat transfer. The experimental results show that: fluid temperature has a great effect on the heat transfer of both nanoparticle suspensions and nanofluids; for both of them, the heat transfer coefficient enhancement comes mainly from the increasing effective thermal conductivity. The surfactant has no influence on the heat transfer. However, it does affect the flow drag characteristic. For suspensions, flow drag is greater than that of water in the laminar flow region, while it is obviously lower than that of water in the turbulent flow region. For nanofluids, the flow drag is greater than that of water in the whole flow region. Fluid temperature has no obvious effect on flow drag of both suspensions and nanofluid.